请教两道PREP2的题，谢谢

huangxiuying

183.   17831-!-item-!-187;#058&011633

If m is a positive odd integer between 2 and 30, then m is divisible by how many different positive prime numbers?(A)

(1) m is not divisible by 3.

(2) m is not divisible by 5

我选E，比如25和29的质因子个数就不一样啊

195.   18858-!-item-!-187;#058&012264

If w, x, y, and z are integers such that w/x and y/z are integers, is w/x+y/z odd?（B）

(1) wx + yz is odd.

(2) wz + xy is odd.

 

愁予

1.25和29的质因子个数一样啊,都是一个.

2.可以设w/x=a,y/z=b,所以w/x+y/z=a+b,又wz+xy=axz+bzx=xz*(a+b)是一个奇数，所以a+b一定是一个奇数。单二可以。单一可以举反例。

huangxiuying

万分感谢，一下子晕了，谢谢LS